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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Rhenium(V)-Imido complexes with potentially multidentate ligands containing the amino group

Booysen, Irvin Noel January 2007 (has links)
The complex trans-[Re(dab)Cl3(PPh3)2] (H2dab=1,2-diaminobenzene) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2dab in ethanol. The ligand dab is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. The complex trans-[Re(ada)Cl3(PPh3)2] (H2ada=2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. Surprisingly, the Re-Cl bond length trans to the Re=N bond is shorter than the two equatorial Re-Cl bond lengths. The reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3- dimethyluracil (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2](ReO4). The X-ray crystal structure shows that the ligand ddd is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated bidentately via the neutral amino nitrogen, which is coordinated trans to the imido nitrogen, and the singly deprotonated amido nitrogen, trans to the iodide. The reaction of equimolar quantities of [NH4(ReO4)] with H2ddd in methanol under reflux conditions led to the isolation of [C12H12N6O4] as only product. The [ReO4]- ion is therefore instrumental in the formation of [C12H12N6O4], and since the product contains no rhenium in any oxidation state, the conclusion is that [ReO4]- catalyses the oxidative deamination of H2ddd. The X-ray crystal structure consists of two centrosymmetric, tricyclic rings, comprising a central pyrazine ring and two terminal pyrimidine rings. The reaction of a twofold molar excess of H2apb (H2apb=2-(2-aminophenyl)-1Hbenzimidazole) with trans-[ReO2(py)4]Cl in ethanol gave the green product of the formulation [ReO(Hapb)(apb)] in good yield. The rhenium atom lies in a distorted trigonal-bipyramidal environment. The two imidazole N(2) atoms lie in the apical positions trans to each other, with the oxo-oxygen and two amido N(1) atoms in the trigonal plane. The complex has C2-symmetry. The two amino groups are singly deprotonated and provide a negative charge each, so that they are coordinated as amides. The oxo group provides two negative charges. In order to obtain electroneutrality for the rhenium(V) complex, the two coordinated imidazole nitrogens provide one negative charge. The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (H3mps=N-(2-amino-3- methylphenyl)salicylideneimine) was prepared by the reaction of trans- [ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The X-ray crystal structure shows that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (which is present in trans- [Re(mps)Cl(PPh3)2](ReO4) as an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen. The [ReO4]- anion has approximately regular tetrahedral geometry. Two significant hydrogen bonds are formed between two of the perrhenyl oxygens and the water of crystallization. The six-coordinated complex cis-[Re(mps)Cl2(PPh3)2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The Xray crystal structure shows that the mps ligand coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen, the neutral imino nitrogen and the phenolate oxygen. The imide and phenolate oxygen coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre, with the two chlorides in cis positions.
32

Syntheses of affinity ligands and monoazaporphyrins

Singh, Jai Prakash January 1987 (has links)
Heme and heme proteins are ubiquitous in nature and play many varied and important biological functions. The biological properties of the heme proteins are dependent on the interaction between the metal and the porphyrin where each is dependent on the other to carry out specific functions. This thesis describes the syntheses of affinity ligands and monoazaporphyrins. The synthesis of the ligand was based on a protoporphyr in-IX derivative substituted on either the 2- or 4-vinyl group. The two isomeric affinity ligands, 73 and 74 (2- or 4- substituted) were synthesized from protoporphyrin-IX di-tert-butyl ester 106b by conversion of the vinyl groups to monoformyl derivatives 122b (or 123b) via the intermediacy of photoprotoporphyrin-IX derivatives. The spacer chain [formula omitted] using a formyl group was extended by Knoevenagel condensation with malonic acid to give monoacrylic acid derivatives 132 (or 133). This chain was further extended by linking an aliphatic diamine (1,3-diaminopropane) to the monoacrylic acid derivatives 132 (or 133) through an acid chloride mediated amide linkage. The Fe(III) and Co(II) complexes of the affinity ligand (73 + 74) were prepared and the tertiary butyl groups were removed by treatment with trifluoroacetic acid at room temperature to give 71 and 72. [formula omitted] An improved synthesis of monoazaporphyrins (5-aza) (see p.iv) is described in this work (section 3.4). Our approach consists of constructing 1,19-dibromo-l,19-dideoxybiladiene-ac dihydrobromides which were subsequently cyclized, to give corresponding monoazaporphyrins in high yields, using dibenzo-18-crown-6 as a phase transfer agent for the transfer of an azide ion. [formula omitted] / Science, Faculty of / Chemistry, Department of / Graduate
33

The synthesis and characterization of some molybdenum, rhenium and rhodium complexes incorporating pyrazolylgallate ligands

Cooper, David Arthur January 1985 (has links)
Several uninegative ligands based on a gallium core and incorporating pyrazolyl groups have been synthesized and their metathesis reactions with molybdenum, rhenium and rhodium halides have been studied. The bidentate pyrazolylgallate ligand [formula omitted] has been incorporated in the complexes [formula omitted]. The unsymmetric tridentate pyrazolylgallate ligands [formula omitted] display a variable reactivity towards molybdenum, rhenium and rhodium precursors. Although no complexes incorporating L⁴ were isolated, L₂ and L₃ were shown to co-ordinate facially in the octahedral complexes [formula omitted] and [formula omitted]. In addition, a meridional co-ordination geometry of L₂ has been structurally characterized in the square planar rhodium(I) complex, L₂Rh(CO). This co-ordinatively unsaturated rhodium(I) species was shown to undergo an interesting oxidative addition reaction with methyl iodide followed by a methyl migration reaction to give a rhodium(III) acetyl derivative. Less predictable products have also been obtained in this study; these include the dimeric species [formula omitted] formed from the reaction of NaL₃ with [formula omitted] and also an unexpected chlorine-containing complex, [formula omitted] from the reaction of [formula omitted]. [formula omitted] the product of the reaction between [formula omitted]. [Formula omitted] (the precursor of Ld) has been structurally shown to possess a novel eight-membered Ga-(N-C-S)₂-Ga ring. / Science, Faculty of / Chemistry, Department of / Graduate
34

Synthesis and characterisation of novel [PtII(phen)(Ln-κS)2] complexes: exploring rare monodentate coordination of disubstituted acylthioureato ligands

Kangara, Edmore F. January 2019 (has links)
A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy, 2019 / This thesis describes a study directed towards the synthesis and full characterization of novel [Pt(phen)(Ln-κS)2] complexes where disubstituted acylthioureato ligands (Ln), (also referred herein as N,N-di(alkyl/aryl)-N’-acylthioureato ligands), coordinate to the platinum(II) metal centre in a monodentate fashion through the sulfur donor atom and establishing the driving factors behind this rare coordination mode. The study included a systematically chosen ligand library where the ligands varied mainly on the electronic influence of acyl substituents balanced with minor steric variations on the amino end of the ligand. [Pt(phen)(Ln-κS)2] complexes were synthesized in excellent yields via a stepwise method where the ligands were first deprotonated using sodium hydride in anhydrous THF and subsequently reacting the resultant solvated salts with the [PtCl2(phen)] precursor under reflux for one hour in a 1:2.2 (precursor/ligand) stoichiometric ratio. The complexes were characterised using FT-IR (ATR) spectroscopy, 1H- and 13C NMR spectroscopy, high-resolution mass spectrometry, UV-vis spectrophotometry, elemental analysis, and single-crystal X-ray diffraction. The complexes were also probed for their solution conformations in correlation with the solid-state structures obtained through single-crystal X-ray diffraction using variable temperature 1H- and 195Pt NMR spectroscopy in order to gain insight into the persistence of intramolecular π-π stacking interactions in solution as a stabilising factor directing the monodentate coordination. This study showed that [Pt(phen)(Ln-κS)2] complexes with acylthioureato ligands bearing aromatic acyl substituents could at least exist in three conformations while complexes with acylthioureato ligands that have non-aromatic acyl substituents could only have one structural conformation at -50 ° C. However, there is no conclusive evidence of the intramolecular π-π stacking interactions in solution at ambient and higher temperatures. Investigations into whether the electronic effects of acyl substituents could influence the nucleophilicity of the other donor sites in the ligands, particularly oxygen, enough to render their reactivity towards platinum(II) ions more preferable was done using conceptual DFT. The study showed that the sulfur donor atom was tenfold more nucleophilic than any other donor atom in the acylthioureato ligands regardless of acyl substituents making it the most probable site to coordinate with platinum(II) ions. Mechanistic insights into how the reaction proceeded were probed through a series of individual experiments that involved the metal precursor, the ligands, the [Pt(phen)(Ln-κS)2] complexes, the byproduct [Pt(phen)(Ln-κO,S)]+ complexes and acids of different degrees of acidity. These experiments showed that the synthetic reaction proceeded most likely via solvolysis of the precursor resulting in a solvento complex and subsequent anation of the solvento complex with disubstituted acylthioureato anions to get [Pt(phen)(Ln-κS)2]. [Pt(phen)(Ln-κS)2] could also be obtained by reacting the cationic byproduct [Pt(phen)(Ln-κO,S)]+ with the ligand after deprotonation with base. It was also shown that the [Pt(phen)(Ln-κS)2] complexes dissociated under different acids resulting in different dissociation products via protonation-anation reactions. The nature of the dissociation products depended on the strength of the acid and the coordinating properties of the acids’ conjugate bases. This coordination mode could be extrapolated to include platinum(II) complexes bearing other co-ligands like bipyridine and triphenylphosphine, however in medium to low yields. A pilot study into the potential antiproliferative activity of [Pt(phen)(L1-κS)2] and [Pt(phen)(L2-κS)2] (where L1 = N,N-di(ethyl)-N’-(1-naphthoylthioureato) and L2 = N,N-di(butyl)-N’-(1naphthoylthioureato) anions) against an A549 lung cancer line showed that these complexes are very active with IC50 values of 6.4 ± 0.9 and 2.4 ± 0.3 μM respectively, killing cancer cells via apoptosis. This study also revealed that these complexes could potentially interact with DNA as a major groove binder. The knowledge obtained through this study should contribute to the fundamental understanding of the coordination chemistry of disubstituted acylthiourea ligands, chemical and physical properties of various platinum(II) complexes bearing disubstituted acylthiourea ligands coordinated in a monodentate fashion and explore possible applications in the fight against cancer. / TL (2020)
35

Complexes of palladium, platinum, rhodium, and iridium containing bridging diphenylphosphide ligands /

Kreter, Paul E. January 1980 (has links)
No description available.
36

A new triphosphine ligand; rhodium, ruthenium, platinum, and iridium complexes of several polyphosphine ligands /

Mazanec, Terry Joseph January 1979 (has links)
No description available.
37

Synthesis and characterization of phosphorus-containing mixed-donor ligands and their complexes with cobalt, iridium, rhodium and platinum /

Uriarte, Richard Joseph January 1978 (has links)
No description available.
38

Synthesis and evaluation of PGM-selective ligands

Gxoyiya, Babalwa Siliziwe Blossom 28 May 2013 (has links)
A series of polydentate POM-selective, sulfur-containing amide ligands have been synthesized from ro-dibromoalkanes and mercaptoacetanilide, The resulting 3,6- dithiaoctanediamides and 3,7-dithianonanediamides, some of which contain a polymerisable group, were all characterized by high-resolution MS, IR, I Hand I3C NMR spectroscopic methods. Various approaches to the polymerisable ligands were explored, the most efficient proving to be the incorporation of an allyl ether moiety in the mercaptoacetanilide. The corresponding Pd(U) and Pt(II) complexes were also prepared from the metal chloride salts and characterized by elemental analysis and spectroscopic methods. The NMR data indicates that both the cis- and transcomplexes were formed, while the IR data indicates cis- coordination of the chlorine . ligands. Molecularly imprinted polymers (MIP's), prepared using platinum(II) mercaptoacetanilide and 3,6-dithiadiamide complexes, showed high selectivity for , , palladium(II) [in the presence of Pt(II), CoCII), Cu(II) and Ni(II)] as determined by . ICP-MS analysis. The more kinetically inert Pt(II) ions however, slowly displaced Pd(II), confirming the Pt(II) selectivity of the MIP's. Solvent extraction studies were conducted to explore the selectivity of the 3,6- dithiaoctanediamides and 3,7-dithianonanediamides for Pd(U) over CoCII), Cu(U) and Ni(II). The ICP-MS data indicate that, in general, equilibration was achieved within ten minutes and that the longer-chain amides were less selective than the shorter-chain analogues. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in
39

Metal ion complexing properties of two dimensional sulfur ligands and their use in neurodegenerative disease

Kissel, Daniel Stephen January 2009 (has links) (PDF)
Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (February 22, 2010) Includes bibliographical references (p. 103-105)
40

Studies towards the development of novel multidentate ligands

Magqi, Nceba January 2007 (has links)
In this study, attention has been given to the design and synthesis of novel multidentate ligands for use in the construction of ruthenium-based metathesis catalysts, and their chelating potential has been explored by computer modelling at the Density Functional Theory (DFT) level. Both Kemp’s triacid (1,3,5-trimethyl-1,3,5-cyclohexanetricarboxylic acid) and D-(+)-camphor have been investigated as molecular scaffolds for the development of such ligands. However selective elaboration of the functional groups in Kemp’s triacid proved difficult to achieve, and the research has focused on the development of camphor derivatives. The synthesis of the camphor-based ligands has involved C-8 functionalisation and ring-opening of the bicyclic system to afford tridentate products. The formation of 9-iodocamphorquinone bis(ethylene ketal) together with the desired product, the 8-iodo isomer, has been confirmed by single crystal X-ray analysis of both compounds. Formation of the 9-iodo analogue has provided new insights into the intramolecular rearrangement of camphor skeleton, and the mechanistic implications have been assessed by coset analysis. Attempts to effect nucleophilic displacement of the 8-halogeno groups by nucleophilic donor moieties proved unexpectedly difficult and, coupled with the susceptibility of the carbonyl groups to nucleophilic attack, has led to the formation of novel tricyclic products, viz., 1,6-dimethyl-3-(2-pyridylamino)-4-oxatricyclo[4.3.0.0[superscript 3,7]]-2-nonanone and 6,7-dimethyl-3-(2-pyridylamino)-4-oxatricyclo -[4.3.0.0[superscript 3,7]]-2-nonanone. However the diphenylphosphine group was successfully introduced at C-8 and oxidative ring-opening of the camphor skeleton has afforded the tridentate ligands, 2-(diphenylphosphinoylmethyl)-1,2-dimethyl-1,3-cyclopentanedicarboxylic acid and 2-(diphenylphosphinoylmethyl)-1,3-bis(hydroxymethyl)1,2-dimethylcyclopentane. One- and two-dimensional NMR and, where appropriate, high-resolution MS methods have been used to characterise the products. Three [superscript 13]C NMR chemical shift prediction programmes, viz., ChemWindow and the MODGRAPH neural network and HOSE (Hierachially Ordered Spherical description of Environment), have been applied to representative compounds to assess their efficacy. While the predicted shifts correlated reasonably well with the experimental data, they proved to be insufficiently accurate to differentiate the isomeric systems examined.

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